; It will play 12 notes of the octave starting at middle C. ;----------------------------------------------------------------------------- ; How to generate sound on the IBM PC : ; ; The 8255 (port 61H) bit 0 controls the 8253 timer ; bit 1 controls the speaker ; ; The output channel 2 from the 8253 timer will be ANDed with the ; speaker control bit in order to turn on/off the speaker. ; ; Timer channel 2 internal count register (port 42h) is loaded in ; two successive OUT operations with the lower byte being loaded first. ; For this to work properly, timer command register has to be loaded first ; with B6H. ; ; Since the input clock to the timer chip is 1.19318 MHz, the counter value ; to generate the frequency X can be calculated by 1193180 / X. ;----------------------------------------------------------------------------- ; CX is used as a note counter with the frequency effectively being ; incremented by a half tone and the corresponding count being loaded ; into the count register on each iteration. ; ; No stack segment is needed for this small program, so don't panic ; when you receive the 'No stack segment' warning. ; ; Arne Asplem 880731 (MASM 4.0) dseg segment ; data segment notes dw 262,277,294,311,330,349,370,392,415,440,466,494 dseg ends cseg segment sound proc far assume cs:cseg, ds:dseg, ss:nothing start: mov ax, dseg mov ds, ax ; set up data segment (DS) reg. xor si, si mov bx, 12 ; note count ; set up timer command register and counter register mov al, 0b6h ; set 8253 command register out 43h, al ; for channel 2, mode 3 nloop: mov ax, 34dch ; low part of clock freq. mov dx, 12h ; hight part of clock freq. div [notes + si] ; get note from data segment out 42h, al ; 8253 command register (low byte) mov al, ah out 42h, al ; 8253 command regsieter (high byte) ; turn on low bits in 8255 output port in al, 61h ; read current value of 8255 port or al, 3 ; clear low bits out 61h, al ; send new value to port ; loop while note is sounding mov cx, 6d60h rpta: loop rpta ; 1/10 sec delay ; turn off speaker, check note count, set up next note xor al, 3 out 61h, al ; turn off speaker mov cx, 0af0h rptb: loop rptb ; 1/100 sec delay inc si ; increment note pointer inc si dec bx ; decrement note counter jnz nloop ; loop until bx = 0 mov ax, 4c00h ; terminate program int 21h sound endp cseg ends end start